Battery gas gauge reset mechanism

ABSTRACT

A gas gauge circuit has a power supply pin, a power return pin, power-on reset capability, and a communications signal pin. A reset control circuit is coupled between the power supply pin and the communications signal pin, or between the power return pin and the communications signal pin. The reset control circuit removes power to the gas gauge circuit in accordance with a control signal asserted on the communications signal pin. Other embodiments are also described and claimed.

An embodiment of the invention is related to electronic mechanisms formonitoring the state of charge of the battery in a battery-operatedcomputer system. Other embodiments are also described.

BACKGROUND

Battery-operated computer systems such as notebook personal computers,portable navigation devices, portable digital media players, and smartphones, have a need for technology that can automatically predict theremaining run time of the device, based on the current state of chargeof its battery. To meet such a need, integrated circuit (IC) developersand manufacturers offer a battery fuel gauge circuit, also referred toas a gas gauge circuit. The basic gas gauge circuit may come in the formof a chip or IC package that is to be integrated in a host device, to beconnected to the terminals of a battery pack of the device. The IC chipor package may be one that is integrated into the battery pack or is ona battery connector board, or it may be located directly on a main logicboard of the device.

The gas gauge circuit contains various analog and digital circuitryneeded to accurately measure battery voltage and/or battery current onan on-going basis (e.g., repeating such measurements every given timeinterval, as the device goes through its typical active and sleep usagecycles). This function is also referred to as a coulomb counter. Thedigital circuitry may include a microcontroller, i.e. a processorcoupled to memory that stores instructions or software code to beexecuted by the processor. The microcontroller executes its programming,to measure or compute various parameters associated with usage of thebattery as part of the device, such as cell voltage, average packvoltage, pack current, capacity change, battery impedance, open-circuitvoltage, and others. It reports such information to a host controller,such as an application processor or power management unit of the hostdevice, through a low overhead bus or interface such as a single wireHDQ serial data interface, a Smart Battery Specification, SBS,interface, or an I²C bus.

Some gas gauge circuits have a watchdog timer integrated in theirdesigns. A watchdog timer monitors a specific periodic signal internalto the gas gauge and looks for its absence. Software running in themicrocontroller of the gas gauge circuit is responsible for repeatedlyacting (e.g., setting a particular bit of a register) to maintain thisperiodical signal. When the periodic signal stops, it is assumed thatthe gas gauge has “hung up” or entered a failure mode software loop.Thus, if the internal timer does not see a signal transition in a setamount of time, it will trigger a reset of the gas gauge (including itsmicrocontroller).

In addition to the watch dog timer, the gas gauge circuit may also havepower-on reset circuitry, which automatically resets the gas gauge whenthe supply voltage provided on its power supply pin cycles, by droppingto a sufficiently low level and then rising to a normal level. Thesupply voltage may drop to zero, for example when the battery pack hasfailed or has been removed from the device.

SUMMARY

As mentioned above, a gas gauge circuit may rely on an internal watchdogtimer to ensure that its functionality can be reset, in the event themicrocontroller of the gas gauge enters a failure mode software loop.This, however, may not provide sufficient protection against otherpotential failure modes of the microcontroller. In accordance with anembodiment of the invention, an external, reset control circuit iscoupled between a power supply pin and a communications signal pin ofthe gas gauge, or between a power return pin and the communicationssignal pin. The reset control circuit automatically removes power to thegas gauge in accordance with an external control signal that has beenasserted on the communications pin. The communications pin, which isnormally used by the gas gauge to report its measured battery parametersto a host controller, is thus also used to respond to or implement asoftware based “hard reset” command from the host controller (which maybe intended specifically for the gas gauge). The command results incycling (off and then on) the external power applied to the gas gauge,thereby achieving a hard reset of the gas gauge, while the battery ispowering the host device in the latter's normal course of operation.Various embodiments of the reset control circuit are described below.

The above summary does not include an exhaustive list of all aspects ofthe present invention. It is contemplated that the invention includesall systems and methods that can be practiced from all suitablecombinations of the various aspects summarized above, as well as thosedisclosed in the Detailed Description below and particularly pointed outin the claims filed with the application. Such combinations haveparticular advantages not specifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention are illustrated by way of example andnot by way of limitation in the figures of the accompanying drawings inwhich like references indicate similar elements. It should be noted thatreferences to “an” or “one” embodiment of the invention in thisdisclosure are not necessarily to the same embodiment, and they mean atleast one.

FIG. 1 is a circuit schematic of an embodiment of the gas gauge resetmechanism.

FIG. 2 shows waveforms for selected signals of the embodiment in FIG. 1.

FIG. 3 is a circuit schematic of another embodiment of the resetmechanism.

FIG. 4 shows waveforms of selected signals from the embodiment of FIG.3.

FIG. 5 is a circuit schematic of a battery monitor module having a resetmechanism.

FIG. 6 shows an example battery-operated computer system being a smartphone in which various embodiments of the invention may be implemented.

FIG. 7 is a block diagram of some of the electronic functional unitsthat make up the mobile device of FIG. 5.

DETAILED DESCRIPTION

FIG. 1 is a circuit schematic of an embodiment of the battery gas gaugereset mechanism. A reset circuit 102 is shown as incorporated in theinterface between a battery 103 (that is to be monitored) and a hostcontroller 104 that is embedded in a mobile device together with thebattery 103. The host controller 103 may be a combination of a processorexecuting software in memory, such as a power management microcontroller executing a power management routine in the mobile device.The term “battery” is used generically here as referring to the mainrechargeable power source unit of the mobile device. FIG. 5 and FIG. 6to be described below show an example of such a mobile device being ahandheld smart phone. The reset circuit 102 may be incorporated into thehost controller-battery interface of other types of mobile devicesincluding, for example, laptop/notebook personal computers, portabledigital media players, and portable navigation devices.

What is shown in FIG. 1 is an electronic circuit for monitoring theenergy of the battery 103 while the latter is connected to power themobile device. The circuit includes a gas gauge circuit 105 whichperforms as a fuel gauge for the battery 103. As explained above, thebasic functions of a gas gauge circuit may include one or more of:measuring battery voltage and/or battery current on an ongoing basis;measuring battery temperature; and monitoring energy output of thebattery and computing a measure of remaining energy in the battery, asthe mobile device goes through its typical active and sleep usagecycles. Such functionality may be achieved by a processor and memorycombination that is supported by various low level analog sensingcircuitry, all of which may be within the gas gauge circuit 105. The gasgauge circuit 105 has a power supply pin Vcc that is coupled to thepositive terminal of the battery 103 through a transistor 106 being, inthis example circuit design, a P-channel field effect transistor (FET)being operated as a switch. A protection fuse 107 is included between aterminal of the battery 103 and the rest of the circuitry in the mobiledevice that is being powered by the battery 103. There is also a powerreturn pin GND (ground) which is coupled in this example directly to thenegative terminal of the battery 103.

Note that the term “pin” is being used in a general sense here asreferring to an integrated circuit's external communications signalcontact (for input or output purposes) or a power contact. This signalor power contact may be that of an IC package or chip carrier, such asthe pin of a leaded or leadless IC package (e.g., a surface-mount ICpackage). Alternatively, “pin” may refer to a wire bonding or flip-chippad or ball of an IC die or chip.

The gas gauge circuit 105 also has a communications signal pin SC towhich part of the reset circuit 102 is coupled as shown. This is not adedicated reset pin, but rather it is used primarily for sending batteryparameter measurements out of the gas gauge circuit 105 (e.g., signalinga computed measure of remaining energy in the battery). Onlyoccasionally is it used for implementing a hard reset of the gas gauge,as described in more detail below.

The gas gauge circuit 105 has power-on reset capability (PORcapability), which refers to a hard reset capability that selfinitializes the circuit 105 in response to power being first applied to,or power being removed from and then reapplied to, the power supplyand/or return pins of the circuit 105. Once POR has been initiated,several typical operations may be performed including initializing aprogram counter that governs the operation of a processor or controllerwithin the gas gauge circuit 105, as well as initializing internalregisters that are used by the processor (not shown).

Before describing details of the rest control circuit 102, various otheraspects of the battery-host interface shown in FIG. 1 are described. Inthe example shown in FIG. 1, the gas gauge circuit 105 communicates withthe host controller 104 through a serial communications line SC thattraverses a battery connector 108. The SC line may be part of a singlewire interface (SWI) or other low overhead bus or interface such as anyof those introduced above in the Background section. More generally, theSC line may support a serial communications data, clock, or controlsignal between the gas gauge circuit 105 and an input or output pin ofthe host controller 104. In this example, the SC line is usedbi-directionally, and for both data and control signals. At the hostcontroller 104, the SC line terminates into a buffer circuit 110 whichallows the single SC line to be shared by both transmit TX and receiveRX pins of the host controller. Alternatively, the SC line may terminatedirectly into a bi-directional pin of the host controller.

In addition to the SC line, the battery connector 108 may also support aVcc line and a GND or ground line, the latter pair being used to supplypower to the main logic board circuitry of the mobile device.

Still referring to FIG. 1, with certain types of batteries, a protectioncircuit 111 may be needed to, for example, detect when the batteryvoltage has dropped to such a low level that the battery 103 should bedisconnected from the main logic board so as not to further dischargethe battery. For example, with lithium ion chemistries, the open circuitcell voltage of a battery should not be allowed to drop below a lowerlimit else damage will result to the battery. Accordingly, theprotection circuit 111 is able to detect such a threshold in the batteryvoltage (by virtue of it being connected across the battery terminals asshown), and will open the transistor switch 112, which in this exampleis on the GND line, thereby disconnecting the battery 103 from the mainlogic board. The protection circuit 111 may be on the battery side ofthe connector 108 as shown. A further protection circuit (not shown) maybe added that automatically disconnects power to the gas gauge circuitwhen the battery voltage is too low (e.g., by blocking current into theVcc pin or out of the GND pin), to prevent the battery from dischargingfurther due to leakage or due to normal operation of the gas gaugecircuit.

Turning now to the reset control circuit 102, in the example of FIG. 1,the circuit 102 is coupled between the power supply pin Vcc of the gasgauge circuit 105 and the latter's communication signal pin SC. In thisexample, the reset circuit 102 is external to the gas gauge circuit 105,rather than being monolithically integrated with the analog and digitalcircuitry of the latter which perform the fuel gauge or batterymonitoring functions. In an alternative embodiment, parts of the resetcircuit 102 may be integrated within the gas gauge circuit 105, thusbeing deemed in that case internal to the circuit 105. The circuit 102includes a transistor 106, used as a switch to turn on and turn offpower from the battery 103 being fed to the Vcc pin. Its gate is pulledup by resistor R1, and can be pulled down by turning on a furthertransistor 113. In this example, transistor 106 is a P-channel FET whiletransistor 113 is an N-channel FET (both being enhancement modedevices). An RC circuit sets the voltage of the control electrode (here,gate) of the transistor 113, which is also used as a switch. R2 isprovided to pull up the gate of the transistor 113 through the SC line.R2 may be fed through the drain of transistor 106 as shown, or it may betied directly to Vcc. The RC circuit is connected to the SC line in aseries configuration as shown. The SC line is also connected to aninverter 114 that is preferably located on the host side of the batteryconnector 108 as shown. The inverter 114 is controlled by an output ofthe host controller 104 (e.g., a GPIO pin). The host controller outputoperates the inverter 114 so that the latter alternatively pulls up theSC line weakly to Vcc, or pulls the SC line strongly down to GND oressentially the battery's negative terminal.

The SC line may thus have two modes of operation, as depicted in thewaveforms of FIG. 2. In its normal mode, the SC line switches betweendifferent logic levels (as the examples “0” and “1” show) to conductbattery monitoring bus transactions, between the gas gauge circuit 105and the host controller 104. This mode is maintained by the hostcontroller driving the inverter 114 to thereby pull up the SC lineweakly or provide a relatively high impedance to the SC line. In thismode, the host controller is said to deassert a gas gauge reset commandon the SC line.

While the SC line is operating in its normal mode, the host controller104 may suddenly decide that hard reset of the gas gauge circuit 105 isneeded, i.e. the gas gauge reset command needs to be asserted on the SCline, because the gas gauge is no longer responding or reporting back tothe host controller 104. To do so, the host controller asserts itsoutput to the inverter 114, thereby, in this example, pulling the SCline down strongly to ground. This is depicted in the waveform of FIG.2. This transition in the SC line may be viewed as the start of the timeinterval t_(RC) which is a time interval proportional to the timeconstant of the RC circuit. During this time interval, the voltage atthe gate of the transistor 113 starts to drop in accordance with the RCtime constant. The voltage drops from a normal “high” level to a “low”level, e.g. smaller than the threshold voltage of transistor 113 so asto turn off transistor 113. The latter action causes the gate voltage oftransistor 106 to immediately rise to a sufficiently high level suchthat transistor 106 is turned off, thereby removing power to the gasgauge circuit 105. This point occurs in the interval indicated in FIG. 2as “GG is powered off”. Thereafter, the host controller output isdeasserted at the end of a predetermined interval identified as a “verylong fixed event” in FIG. 2. At that point, the SC line is released fromGND, thereby allowing the pull up R2 to charge the RC circuit so thatthe gate voltage of transistor 113 rises back up to its original, highlevel. The latter, of course, turns the transistor 113 back on, therebypulling down the gate electrode of transistor 106 to a sufficiently lowlevel as to also turn on the latter transistor, thereby applying powerback to the gas gauge circuit 105. In FIG. 2, this is indicated by thetime interval described as “GG is powered on and is resetting”, becausenow the gas gauge circuit is undergoing a conventional power-on resetcycle. This may complete the execution of the command of the hostcontroller 104, to perform a hard reset of the gas gauge circuit 105.Normal communications between the host controller 104 and the gas gaugecircuit 105 resumes on the SC line following the latter time interval,again as depicted in the waveforms of FIG. 2. Thus, asoftware-controlled (by the host controller) hard reset of the gas gaugecircuit may be achieved, without adding an additional pin to the batteryconnector 108.

Considering the embodiment of FIG. 1 and the waveform in FIG. 2 again,it should be understood that the reset control circuit 102 removes powerto the gas gauge circuit 105, in accordance with a control signal thatis asserted on its communications pin SC. In this case, the assertedcontrol signal embodies a “very long” fixed event, namely one where theSC line is kept at the logic “0” level for an interval of time that ison the order of t_(RC). More specifically, the very long fixed event(and hence t_(RC)) is selected, by the developer or manufacturer of thebattery monitoring circuit, to have a time interval that is longer thanthe longest logic level that is possible for a transaction on the SCline, in order to distinguish the reset command from normal batterymonitoring bus transactions on the line. Thus, the asserted timeinterval for the reset command (asserted by the host controller on theSC line) should be selected based on the communications protocol usedfor transactions on the SC line.

Turning now to FIG. 3 and FIG. 4, another embodiment of the invention isshown in which the control signal that is asserted on the communicationspin SC is of a different type. In particular, the control signal isasserted in this case by overdriving the SC pin above the normaltransaction signal swing on the pin. In the example waveforms of FIG. 4,the overdrive event is a pulse that rises to the level of the batteryvoltage, whereas normal battery monitoring bus transactions on the SCline have a much lower voltage swing as shown. The overdrive event alsoresults in a hard reset of the gas gauge circuit 105, albeit using adifferent type of reset circuit 302, as depicted in FIG. 3.

Referring to the circuit schematic of FIG. 3, the reset circuit 302 ofthis embodiment shares the same transistor 106 and pull up resistor R1of the embodiment of FIG. 1, uses a separate transistor 313 in serieswith the Vcc pin to alternatively pass or block the current from thebattery supply line. The latter transistor 313 is operated as a switchby tying its control electrode to the pin or SC line, which aftertraversing the battery connector 108 is coupled to the drain electrodeof a P-channel transistor 314 that is also operated as a switch. Thelatter transistor is controlled by a N-channel transistor 315 whose gateelectrode is driven by the GG reset output pin of the host controller104. Using such a circuit, the host controller 104 can command a hardreset of the gas gauge circuit 105 over the SC line, by asserting its GGreset output to turn-on transistor 315, which turns-on transistor 314.The latter pulls up the SC line strongly to the Vcc or battery powersupply line voltage, thereby turning off the P-channel FET which is thetransistor 313. The latter action, of course, cuts off current to theVcc pin of the gas gauge circuit 105, thereby powering off the gas gaugecircuit (see the time interval described as “GG is powered off” in FIG.4). After a relatively short time interval (which may be based on thehard reset requirements of the gas gauge circuit 105), the hostcontroller deasserts its GG reset output, which starts the time intervaldescribed as “GG is powered on and is resetting”. Deasserting the outputof the host controller reverses the above operations on the transistors315, 314 and 313, thereby reapplying power back to the Vcc pin of thegas gauge circuit 105. The host controller output thereafter remainsdeasserted, and the gas gauge circuit 105 upon exiting its power-onreset cycle resumes with its battery monitoring and normal bustransactions on the SC line.

The reset mechanisms described may be incorporated into a batterymonitor module 500, such as the one depicted in FIG. 5. The module 500may have a separate carrier substrate or circuit board, that is to beconnected between the battery 103 and a main logic board of the mobiledevice. The carrier substrate has a supply rail that couples a “+”battery side terminal to a Vcc terminal on the main logic board side,and a return rail that couples a “−” battery side terminal to a GNDterminal in the main logic board side. A battery monitor circuit 503resides on the carrier substrate. The monitor circuit 503 may be the gasgauge circuit 105 described above, with the addition of one or moreprotection circuits that protect the battery from being discharged totoo low of a battery voltage level, by automatically disconnecting thegas gauge circuit or disconnecting the power or supply rails (therebyisolating the battery). The module 500 also has a reset control circuit504 that is coupled between the communications signal pin SC of themonitor circuit 503 and either the power supply or return rails. In thisexample, the reset circuit 504 is shown as being able to disconnect themonitor circuit 503 through the latter's GND pin, by breaking thecurrent path from the GND pin to the return rail, in response to the gasgauge reset command being asserted on the SC line.

In yet another embodiment of the invention, the battery monitoringcircuitry, which includes the gas gauge circuit 105, the reset circuit102 or 302, and any additional protection circuits (such as inaccordance with the schematic of FIG. 1 or that of FIG. 3, for example),can be implemented entirely on the main logic board side of the batteryconnector 108. In that case, for purposes of the reset mechanismdescribed here, only the Vcc and GND lines may be needed in the batteryconnector 108 because the circuit components that make up the resetcircuit would essentially reside on the main system or main logic boardof the mobile device (located to the right of the battery connector 108,depicted in FIG. 1 and FIG. 3).

Turning now to FIG. 6, this figure shows a view of the front of anexample mobile device 200 in which the battery gauge reset mechanism maybe implemented. The device 200 shown and described here has similaritiesto the Iphone™ device by Apple Inc. of Cupertino, Calif. Alternatively,it could be another portable or mobile, handheld multi-functionelectronic device or smart phone that has some or all of thefunctionality described below. The device 200 in this case has a fixed,single piece housing, sometimes described as a candy bar or chocolatebar type, in which the primary mechanism for visual and tactileinteraction with the user is a touch sensitive display screen 252. Analternative to this type of mobile device is one that has a moveable,multi-piece housing such as a clam shell design or one with a sliding,physical key pad as used by other smart phone manufacturers. The touchscreen 252, or in other cases a simple display screen, will displaytypical smart phone features, such as visual voicemail, web browsing,email functions, digital camera pictures, as well as others. The examplein FIG. 6 shows the touch screen 252 displaying the home or main menu ofa graphical user interface that allows a user of the device 200 tointeract with various application programs that can run in the device200. The home menu displays icons or graphical images that representapplication programs, files, and their associated commands as shown.These may include windows, fields, dialog boxes, menus, virtual buttons,cursors, scrollbars, etc. The user can select from these graphicalimages or objects by touching the surface of the screen 252 with herfinger, in response to which the associated application program will belaunched.

The device 200, in this case, also has a wireless telephony functionthat enables its user to receive and place audio and/or video calls. Atthe upper end of the housing, an opening 210 is formed through whichdownlink audio during a call is emitted from an earpiece speaker 220. Ata bottom end portion of the device 200, a microphone 216 is located topickup the near end user's speech, which is then transmitted in anuplink signal to the far end user, during the call. In some cases, thedevice 200 also has a speakerphone speaker 218 built into the devicehousing, which allows the user to conduct a call without having to holdthe device 200 against her ear. A proximity sensor 254 (see FIG. 7) maybe integrated in the mobile device 200, so as to detect proximity of thetouch screen 252 to the user's face or head, and thereby automaticallydisable input through the touch screen 252 during a handset mode call.

FIG. 7 depicts an example architecture for the hardware and softwarecomponents that enable the various functions of the device 200. Thedevice 200 has several built-in electro-acoustic transducers, includingthose introduced above, namely a microphone 216 for pickup of the user'sspeech, a speakerphone speaker 218, and an earpiece speaker 220. Theanalog acoustic transducer signal from the microphone 216 is input to anaudio codec 214, whereas output audio signals are provided by the codec214 to the speakers 220, 218. The codec 214 thus acts as an interface tothe analog input of the microphone 216 and the analog outputs of thespeakers 218, 200, by providing any analog amplification, analog signalconditioning, and analog to digital conversion, as well as digital toanalog conversion, as needed to deliver drive signals to the speakers218, 220 and digitize the pickup signal from the microphone 216. Thecodec 214 may be a separate IC package.

The codec 214 may be configured to operate in different modes, inaccordance with programming or control signals supplied by a processor150 (also referred to as an applications processor). Communicationsbetween the codec 214 and the processor 150 may be over an embeddedcomponent bus, such as an I²C bus. In one mode, referred to as mediaplayer mode, the device 200 may be operating as a digital media player(e.g., an MP3 player that is playing back music files stored in thedevice 200). Audio output from the codec 214 in that case may bedirected to the speakerphone speaker 218 or an audio jack 228 to which aheadset plug (not shown) is connected. In another mode, referred to ascall mode, the device 200 is operating as a mobile telephony device,e.g. allowing its user to be in a real-time audio conversation with afar end or remote user. In that mode, the codec 214 may act as an analogpass through, simply forwarding the microphone pickup signal to a baseband processor 52 which the latter converts into an uplink signal, andforwarding a downlink signal from the base band processor 52 to thespeaker 218 or 220.

The base band processor 52 is part of an interface that receives adownlink signal from and sends an uplink signal to a cellularcommunications network, using the cellular network RF circuitry 54 andits associated antenna 62. The base band processor 52, which may be aseparate IC package, may have a downlink input port and an uplink outputport, both of which may be in an intermediate frequency band, e.g.around 26 MHz. Alternatively, the downlink and uplink ports may be atbase band frequency range, such that a direct frequency conversion isperformed by the RF circuitry 54, relative to the RF carrier frequencyat the antenna 62. The antenna 62 is used for long range wirelesscommunications, with the nearest cellular network base station, forexample. In short range wireless communications (e.g., in accordancewith a Bluetooth protocol and/or a wireless local area networkprotocol). The antenna 62 may be used to communicate in a 3G oruniversal mobile telecommunications system, UMTS, band, such as around850, 900, 1800, and 1900 MHz. The RF circuitry 54 performs the neededdown conversion and up conversion, from the UMTS or other cellularnetwork band to the intermediate frequency or base band frequency, atthe input or output port of the base band processor 52. The RF circuitry54 may thus include various active and passive RF signal processingcomponents, including frequency down converter and up converter, RFpower amplifiers, and RF filters.

The base band processor 52 may perform known cellular network base bandprocessing tasks, including cellular protocol signaling, coding anddecoding, as well as signaling with the external RF circuitry 54. Thistogether with the RF circuitry 54 may be viewed as part of the radiosection of the device 200. The base band processor 52 may beprogrammable, in accordance with software that has been encoded andstored in its associated non-volatile memory 154. Permission to accessthe cellular network may be granted to the near end user in accordancewith a subscriber identify module, SIM, card that is installed in themobile device 200 to connect with the SIM connector 258.

The device 200 may also have further wireless communications capability,to provide a global positioning system, GPS, service, a Bluetooth link,and a TCP/IP link to a wireless local area network. To this end, aBluetooth transceiver 160 is provided together with a wireless localarea network, WLAN, transceiver 164, which provide additional wirelesscommunication channels for the device 200. These two channels may sharean antenna 63 for short range wireless communications (e.g., inaccordance with a Bluetooth protocol and/or a wireless local areanetwork protocol). An RF diplexer 188 has a pair of RF ports that arecoupled to the antenna 63. One of the RF ports is used for GPS services,which a GPS receiver integrated circuit 156 uses to obtain GPS data thatallows the mobile device 200 to locate itself to its user. The other RFport of the diplexer 188 is coupled to an RF front end 172 that combinesBluetooth and WLAN RF signals.

The cellular network, GPS, Bluetooth, and WLAN services may be managedby programming the processor 150 to communicate with the base bandprocessor 52, Bluetooth transceiver 160, and wireless transceiver 164through separate, component buses. Although not shown, there may also beseparate component buses connecting the base band processor 52 to theBluetooth transceiver 160 and WLAN transceiver 164, to enable the lattertransceivers to take advantage of the audio processing engine availablein the base band processor 52, to, for example, conduct a wireless voiceover IP call (using the WLAN transceiver 164) and to allow the near enduser to conduct the call through a wireless headset (using Bluetoothtransceiver 160).

The so-called power hungry components of the mobile device 200 mayinclude the base band processor 52, the processor 150, the touch screen252, and the transmit RF power amplifiers that are part of the RFcircuitry 54. These are coupled to be monitored by a power managementunit 248. The power management unit 248, which is an example of the hostcontroller 104 described above, may monitor power consumption byindividual components of the device 200 and may signal power managementcommands to one or more of the components as needed so as to conservebattery energy and control battery temperature.

Other lower level hardware and functionality of the mobile device 200include an on/off or reset button 250, a vibrator 274 used to indicatethe ringing signal of an incoming call, an audio ringer, a physical menubutton, and a volume up/down button (collectively referred to as circuitelements 272 which may be coupled to output pins of the processor 150 asshown). The mobile device 200 may also have a dock connector 230 thatcommunicates with a USB port of the processor 150, allowing the device200 to, for example, synchronize certain files of the user withcorresponding files that are stored in a desktop or notebook personalcomputer of the same user. The dock connector 230 may also be used toconnect with a power adapter or other electricity source for chargingthe battery (via the battery connector 108).

In a further embodiment, the mobile device 200 may have digital cameracircuitry and optics 264 that are coupled to the processor 250, enablingthe mobile device to be used as a digital still or video camera.

Having described the lower level components of the mobile device 200, abrief discussion of the higher level software functionality of thedevice is in order. As suggested above, the device 200 may beessentially considered to be a computer whose processor 150 executesboot code and an operating system (OS) stored in the memory 262 withinthe device. Running on top of the operating system are severalapplication programs or modules that, when executed by the processor150, manage at a high level the following example functions: placing orreceiving a call (phone module); retrieving and displaying emailmessages (mail module); browsing the web (browser module); and digitalmedia playback (iPod™ player module). Additional applications or widgetsmay be executed by the processor 150, such as those depicted in FIG. 6,including a clock function, SMS or text messaging service application, aweather widget, a calendar application, a street map navigationapplication, and a music download service application (the iTunes™service).

The invention is not limited to the specific embodiments describedabove. For example, a mobile device (in which the reset mechanismsdescribed above can be implemented) need not have the exact hardware andsoftware architecture depicted in FIG. 6 and FIG. 7. In particular, theGG reset input/output pin shown within the power management unit 248could alternatively be part of another “host controller” in the device200, e.g. the combination of the processor 150 and memory 262.Accordingly, there are other embodiments within the scope of the claims.

1. An electronic circuit for monitoring a battery, comprising: a gasgauge circuit having a power supply pin, a power return pin,power-on-reset capability, and a battery parameter output communicationssignal pin; and a reset control circuit coupled between (a) the powersupply pin or the power return pin and (b) the communications signalpin, to remove power to the gas gauge circuit in accordance with acontrol signal asserted on the communications pin, wherein thecommunications signal pin is an output to send battery monitoring datato a separate host controller; wherein the control signal is received onthe signal pin in a reverse direction; and wherein in response toreceiving the control signal on the communications pin, the resetcontrol circuit is to cut off current to the power supply pin from abattery supply line, or cut off current from the power return pin to abattery return line.
 2. The electronic circuit of claim 1 wherein thegas gauge circuit comprises a processor and memory, the memory storesinstructions that when executed by the processor (a) monitor energyoutput of a battery, (b) compute a measure of remaining energy in thebattery, and (c) signal the computed measure to a host processor usingthe communications pin.
 3. The electronic circuit of claim 2 wherein thecommunications pin is a serial communications protocol signal pin. 4.The electronic circuit of claim 2 wherein the reset control circuit isto remove power to the gas gauge, by cutting off current to the powersupply pin from a battery supply line.
 5. The electronic circuit ofclaim 4 wherein the reset control circuit is to assert the controlsignal on the communications pin by overdriving the communications pin,in response to a command from the host processor of a mobile device. 6.The electronic circuit of claim 5 wherein the reset control circuitcomprises a transistor switch coupled to pass current from the batterysupply line to the power supply pin, a control electrode of thetransistor being coupled to the communications pin.
 7. The electroniccircuit of claim 6 wherein the reset control circuit is to overdrive thecommunications pin so that the control electrode reaches a voltage ofthe battery supply line to thereby turn off the transistor switch. 8.The electronic circuit of claim 2 wherein the reset control circuit isto remove power to the gas gauge, by cutting off current from the powerreturn pin to a battery return line.
 9. The electronic circuit of claim8 wherein the reset control circuit is to assert the control signal onthe communications pin, by maintaining a fixed logic low level on thecommunications pin for a time interval that is longer than the longestlogic low level for a transaction on the communications pin.
 10. Theelectronic circuit of claim 1, wherein as a result of receiving thecontrol signal asserted on the communications pin, the reset controlcircuit is to remove power to the gas gauge circuit without resetting orremoving power to the separate host controller.
 11. The electroniccircuit of claim 1, wherein as a result of receiving the control signalasserted on the communications pin, removing power to the gas gaugecircuit.
 12. The electronic circuit of claim 1, wherein removing powerto the gas gauge circuit comprises removing power only to the gas gaugecircuit.